Several in vivo measurement systems are known in the art. They include swallowable electronic capsules which collect data and which transmit the data to a receiver system. These intestinal capsules, which are moved through the digestive system by the action of peristalsis, are used to measure pH (“Heidelberg” capsules), temperature (“CoreTemp” capsules) and pressure throughout the gastro-intestinal (GI) tract. They have also been used to measure gastric residence time, which is the time it takes for food to pass through the stomach and intestines. These intestinal capsules typically include a measuring system and a transmission system, where a transmitter transmits the measured data at radio frequencies to a receiver system.
Endoscopes are other types of devices that obtain images from the gastro-intestinal tract. There are currently two types of endoscopes. Fiber-optic endoscopes are pushed through the GI tract and use a fiber optic waveguide to transmit a light signal from the area of interest to electronics located outside the patient's body. Video endoscopes place an electronic camera at the area of interest and transfer the video data through a flexible cable to electronics located externally.
U.S. Pat. No. 5,604,531, assigned to the common assignee of the present application and incorporated herein by reference, teaches an in vivo measurement system, in particular an in vivo camera system, which is carried by a swallowable capsule. In addition to the camera system there is an optical system for imaging an area of the GI tract onto the imager and a transmitter for transmitting the video output of the camera system. The overall system, including a capsule that can pass through the entire digestive tract, operates as an autonomous video endoscope. It images even the difficult to reach areas of the small intestine.
Reference is now made to FIG. 1 which shows a block diagram of the in vivo video camera system described in U.S. Pat. No. 5,604,531. The system captures and transmits images of the GI tract while passing through the gastrointestinal lumen. The system contains a storage unit 19, a data processor 14, a camera 10, an image transmitter 8, an image receiver 12 (often an antenna array), which usually includes an antenna array, and an image monitor 18. Storage unit 19, data processor 14, image monitor 18, and image receiver 12 are located outside the patient's body. Camera 10, as it transits the GI tract, is in communication with image transmitter 8 located in capsule 6 and image receiver 12 located outside the body. Data processor 14 transfers frame data to and from storage unit 19 while the former analyzes the data. Processor 14 also transmits the analyzed data to image monitor 18 where a physician views it. The data can be viewed in real time or at some later date.
The number of pictures that need to be taken and which must be analyzed by the attending physician is great. Assuming a minimum of two images per second and a four to five hour dwell time in the GI tract, 30,000 images would be required during the transit of the GI tract by the capsule. If 20 frames per second (fps) are displayed as is standard, the physician would need about 30 minutes to examine the images of the entire GI lumen.
PCT Application PCT/IL98/00608, published as WO 99/30610 and Israeli Application 122602 assigned to the common assignee of the present application and incorporated herein by reference, recite a method for reducing the number of frames captured by an in vivo camera, thereby extending its life. The method discussed in the aforesaid applications requires disconnecting the camera 10 from the power source when motion (velocity) is below a certain threshold value.